CITRATE COMPLEX OF NICKEL

Citrate complex of nickel has been investigated by pH titration method within the pH range 2.5 to 7. A neutral complex C is formed at lower pH due to the reaction of a nickel ion and citric acid with the simultaneous liberation of two protons. The equilibrium constant of this reaction has been found to be 7.97 x 10^-5 This complex with increase in pH dissociates to a H⁺ ion and complex C₁, the dissociation constant being 1.75 x 10^-1. At still higher pH the complex C₁^- farther dissociates like a monobasic acid to C₂^2- and H⁺. The dissociation constant of the latter reaction is = 35 x 10^-5, The structures of these complexes have been discussed.